####018006618#### FXUS65 KBOU 240936 CCA AFDBOU Area Forecast Discussion...CORRECTED National Weather Service Denver/Boulder CO 336 AM MDT Wed Apr 24 2024 .KEY MESSAGES... - Slight Risk of severe thunderstorms Thursday, east of a line from Sterling to Akron, including large hail, damaging winds and isolated tornadoes. A marginal risk south and west of this area. - Cool and unsettled Friday into the weekend, with accumulating moderate snowfall in the mountains, widespread rain showers over the plains && .SHORT TERM /Through tonight/... Issued at 330 AM MDT Wed Apr 24 2024 One fairly quiet weather day today before we get more active Thursday through much of the weekend. Satellite and radar shows a few showers lingering in these early morning hours over the far northeast plains, while ridging is starting to take hold with clearing skies building in from the southwest. The ridging and warm advection will bring a bump in temperatures today, with much above normal readings expected. Most of the plains and I-25 Corridor will reach the mid to upper 70s (slightly cooler far east), while mountain areas will enjoy 50s and 60s. There is slight drying aloft moving into the forecast area, but temperatures are warming and models still show a bump in instability this afternoon. Thus, despite the upper ridging we still expect isolated showers and storms late this afternoon and evening, favoring areas in the mountains and across the plains closer to the Wyoming and Nebraska borders. We can't totally rule out isolated high based showers farther south along a surface convergence zone, but that would be quite weak and only brief sprinkles/very light rain. For tonight, low level moisture advection begins in earnest across the northeast plains as low level flow turns south/southeast. That will draw in the current airmass in the Texas Panhandle with dewpoints rising into the mid 40s overnight. Stratus and patchy fog expected to develop, with higher ridges being more prone to advection fog. It will also be breezy to windy at times over the Palmer Divide and eastern plains today and tonight, with gusts of 30-40 mph expected at times. Lighter winds elsewhere. && .LONG TERM /Thursday through Tuesday/... Issued at 330 AM MDT Wed Apr 24 2024 On Thursday, a couple severe thunderstorms will be possible over the northeast plains. The first short wave trough will move across CO around 00z Friday, with moderate mid and upper level QG ascent ahead of the trough in the afternoon. At the surface, an west- east oriented warm front will move off the Palmer Divide, with southeast winds north of the front advecting low level moisture in the plains. Fog and/or stratus will be an issue through Thursday morning north fo the front. Model soundings indicate ML 100mb CAPE around 1000-1200 j/kg in the afternoon, with 0-3km storm relative helicities of 150-200 m2/s2. The combination of instability/shear appears to be sufficient to warrant a slight risk of severe thunderstorms, primarily east of a line from around Sterling to Akron. Large hail, damaging wind as well as a tornado or two may be possible. West and south of this line, the risk will be more on the marginal side. Timing wise, it appears that the storms will initiate along the warm front around 21z then move northeast through 03z. By 12z Friday, the upper low will be over southwest NE, with wrap around moisture associated with northwesterly flow on the west side of the exiting trough, impacting the plains through the day. There will be enough moisture and instability around for snow showers to in the mountains, and rain showers/isolated tstms over the plains. The best coverage for showers would appear to be to the north and east of Denver on Friday. By Friday night, a short wave ridge will move across the forecast area which may allow for a brief decrease in precipitation intensity overnight but not necessarily coverage as the impact (subsidence) from the ridge will be short lived. On Saturday, the next trough will move out of the Great Basin and into central CO by 00z Sunday, then exiting into southwest NE/northwest KS by 12z Sunday. Moderate mid/upper level QG ascent will be over northeast CO through the day Saturday, then decrease from west to east Saturday night. In this time, the models generate anywhere from 6-14 inches of snow in the higher mountains. The main window will be from 06z Saturday to 00z Monday. If this trend continues, then either a Winter Storm Watch or Advisory may be issued. Light snow accumulations can also be expected over the Palmer Divide Saturday night into Sunday morning. Across the northeast plains, the pops will start to decrease Sunday afternoon into Sunday night. Total qpf generated by the models will be around 2 inches, with the highest amounts in the mountains, and across the northeast plains towards the WY and NE. By early next week, the trough will have exited to the east but enough moisture will be available at least in the mountains for a chance of residual showers on Monday, then dry and warmer weather returns on Tuesday. && .AVIATION /06Z TAFS through 06Z Thursday/... Issued at 1135 PM MDT Tue Apr 23 2024 VFR through the TAF period with generally SCT-BKN mid-level clouds. Showers were exiting the area and winds were now settling back to the normal overnight flows. There's still a small chance of variable winds for the next few hours, but overall south/southwest winds should prevail through 15Z for KDEN and KAPA, with northwest/west at KBJC. After that, there is a tendency for southwest winds at KDEN and KAPA, but can't rule out a period of variable winds again. In fact, some guidance keeps it variable through the entire day, while pressure patterns and daytime heating would suggest more of a southeasterly flow. Therefore, we'll keep that SE wind in the TAF for consistency...but winds and persistence will be something to watch. A couple of high-based showers are possible again after 21Z Wednesday, but coverage at this point looks sparse enough that VCSH wasn't included. If anything does develop in the area, VRB wind gusts to 30 kts possible given the dry sub-cloud layer and DCAPE near 1000 J/kg. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...DB LONG TERM...Cooper AVIATION...DB ####018005372#### FXUS65 KLKN 240937 AFDLKN Area Forecast Discussion National Weather Service Elko NV 237 AM PDT Wed Apr 24 2024 .SYNOPSIS...Period of active weather including breezy to gusty winds continues with accumulating rain showers and thunderstorms in the forecast thru at least Friday. Drier beginning Saturday and into early next week though weather reamins unsettled with contniued breezes and low probabilities for rain across portions of northern Nevada. && .SHORT TERM...Today through Thursday Night Rain showers and thunderstorms become more widespread today in response to an upper low moving into SoCal from the Pacific. Greatest activity remains generally focused along a band stretching from northwest Nye County to northern Elko County as a modest boundary resides across the area. The highest precipitaion totals are forecast to reside in this region with valley totals tallying between 0.10" and 0.25". Liquid totals across the high terrain indicated to be around 0.50". Main concerns will be lightning, localized gusty winds, and small hail associated with thunderstorms. Some concern also for sharp rises in faster responding streams and creeks under prolonged or heavier rain showers, especially with flowages running high thanks to seasonal snow melt. Showers and thunderstorms expected to persist overnight but overall activity will dissipate. Afternoon breezes throughout the forecast area will also be present with gusts 20 to 25 mph. Daytime high temperatures reside mostly in the 60s with overnight lows in the low 30s to low 40s. Continued active weather and concerns Thursday with rain showers, thunderstorms, and high elevation snow expected as the low moves east into the four corners region. By Thursday night the next upper wave begins to bring a progressive cold front through the region with an increase in shower activity in conjunction with the front. Greatest rain totals between Thursday and Thursday night look to be concentrated across the eastern half of the forecast area with valley totals between 0.25" and 0.50" expected. Around 1" of liquid equivalent expected for the high mountains with a few inches of snow also likely. Breezy west winds in place Thursday as well with gusts 20 to 30 mph. Daytime high temoperatures will be in the mid 50s to mid 60s with overnight lows mostly in the 30s. && .LONG TERM...Friday through Wednesday A series of storm systems associated with a large scale troughing pattern across the western U.S. will continue into the weekend, bringing more widespread rain and mountain snow to the area. Rain accumulations across the state will range from 0.25” to 0.75” for the valleys and passes, with the heaviest amounts across the eastern half of NV. The mountain ranges above 8000 feet could see up to 6 to 12 inches of snow through Saturday. Temperatures expected to cool down given the increasing cloud cover and precipitation, with highs in the 50s to 60s along with breezy conditions each afternoon. Overnight lows will generally be in the 30s to 40s, lowering into the 20s to 30s for the weekend. Isolated to scattered showers may persist mainly across northern NV heading into early to mid next week, while dry conditions expected for the rest of the CWA. && .AVIATION...Look for mainly VFR conditions for the next 24 hour period. VCTS will be possible for the afternoon at the KEKO and KBAM terminals. Winds will generally be less than 20 knots across the northern sites with winds SW10-15G25KT for KELY and KTPH during the afternoon. KWMC is AMD NOT SKED due to communication disruption. && .HYDROLOGY...Elevated flows continue across many streams, creeks, and rivers across northern and central Nevada due to snow melt. Active weather including valley and mid-elevation rain showers are expected thru at least Friday. Wetting rains are expected and awareness should be exercised for sharp rises in faster responding streams and creeks under prolonged or heavier rain showers, especially with flows running high due to seasonal snow melt. Cooler temperatures are also expected the next few days, which will likely slow high elevation snow melt. The Bruneau River is currently in action stage, nearing minor flood stage. The river will likely rise further in the coming days. The Humboldt River at Battle Mountain is currently in action stage and is expected to continue to reside in action stage for the next several days. The Owyhee River near Wildhorse is currently in action stage and expected to gradually rise in the coming days. The river is forecast to reach minor flood stage by this weekend. The Owyhee River near Mountain City is currently in minor flood stage. The river is forecast to remain in minor flood stage over the next several days. Wildhorse Dam is currently in action stage and is expected to continue to reside in action stage for the next several days. The Humboldt River at Comus is currently in action stage and is expected to continue to reside in action stage for the next several days. && .LKN Watches/Warnings/Advisories... None. && $$ 92/90/86 ####018009509#### FXUS63 KGLD 240939 AFDGLD Area Forecast Discussion National Weather Service Goodland KS 339 AM MDT Wed Apr 24 2024 .KEY MESSAGES... - Significant severe weather is possible Thursday for most of the area with the main threats being tornadoes and very large hail. The threat is conditional as a cap could prevent storms from forming. - A Fire Weather Watch is in effect Thursday south of I-70 and west of Highway 25 for low humidity and strong winds. - Blowing dust is also possible Thursday afternoon for near and south of the I-70 corridor. && .SHORT TERM /THROUGH FRIDAY NIGHT/... Issued at 334 AM MDT Wed Apr 24 2024 For today, a fairly similar day to yesterday is in store with a mix of clouds and sun through the day today and highs around 70. Showers and storms would then return to the area this evening and overnight as a shortwave moves through the larger flow. The main difference today is that winds will be a bit stronger around 20 to 25 mph and from the south which will help bring moisture into the area. For tonight, will need to watch for fog in the area with the moisture advection, especially since winds are forecast to have a slight easterly, upslope component overnight. The other thing to watch will be the potential for a second round of stronger storms just before sunrise as some guidance suggests that there could be some elevated instability. Even if tapped into, it is unlikely severe storms would occur, but CAPE just shy of 1000 J/KG and shear around 45-55 kts could allow hail to form. Tomorrow is still forecast to be an active day, but will depend on dryline placement and how long cloud cover lingers. Guidance has come into better agreement on the low and dryline setting up on KS/CO border in the area by the late afternoon and early evening hours. This would leave most of the area in cloud cover (and potentially fog) until the early afternoon hours. Some locales closer to Central Nebraska and Kansas may have cloud cover persist through the day which would limit temperatures to the 60's. Meanwhile, clouds would clear beginning from East-Central Colorado. This would allow these locales to warm into the 80's and also dry out as the dryline advances. With this and the approach of the low pressure system strengthening the winds, have opted to issue a Fire Weather Watch for south of I-70 and west of Highway 25 where critical fire conditions could be met late in the afternoon. The main uncertainty is how fast will the dryline advance and will it be enough to lower RH for 3 hours. Also later in the afternoon tomorrow, will need to watch for a blowing dust threat generally along and south of I-70. Local research suggests that winds will become strong enough around 21Z from the south to start generating some blowing dust. It looks to be unlikely that there'd be a thick plume of dust or brownout conditions (except right next to source regions) as lapse rates around 2km are forecast to still be around 9 C/KM which could allow dust to mix out further and not become concentrated. The main threat for Thursday is the chances for severe weather. With the moisture advection and the chance for multiple boundaries to be in the area due to the low pressure system, storms will have the possibility to form. If they do form, the biggest threats would be large hail that could exceed 2" (CAPE around 2500 J/KG and effective shear around 55-60kts would allow for longer lived supercells) and tornadoes. The tornado threat has increased with the latest forecast packages as guidance suggests that there will be ample 0-1km shear and SRH along with low LCLs. The dryline and a potential warm front across NW Kansas could also serve as focuses and a genesis point for tornadoes with the NAM 3km suggesting that any dryline initiated storms would be well favored to produce tornadoes (STP near 6). The main uncertainty for severe storms is can they form and if they do, how far can they move east before diminishing. Guidance has been consistent with a cap (convective inhibition) developing around the 800-700mb level largely due to the cloud cover keeping near surface temperatures cooler. If the CAP erodes near the dryline or any boundary, storms should have enough forcing and instability to develop. Significant hail would be more likely if the cap is weaker than forecasted and is then overcome during the afternoon hours. As for how long severe storms would last, the more of the area under cloud cover until the mid to late afternoon hours, the more of the area with little to no instability to sustain the storms which would cause them to dissipate as they move east. In summary, significant severe weather is possible tomorrow unless most of the area can stay under cloud cover until the late afternoon hours or the cap is stronger than forecast. Going into the overnight hours, the low is forecast to begin lifting north and east across the area which could temporarily stop precipitation if the dry air is pulled north with it. The night hours would then see winds slowly shift to out of the northwest with lows in the 40's and 50's. Friday, wrap around precipitation is possible through the day, especially if the low elongates to the south and slows down. Winds should strengthen behind the system, but currently have gusts around 50 mph with sustained speeds around 25 to 30 mph. There doesn't seem to be much of a chance of the winds getting to High Wind criteria looking at how deep the low would get in ensemble members, but it would be breezy for sure. Temperatures would likely stay near average in the 60's and 70's with little to no cold air advection behind the system. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Issued at 120 AM MDT Wed Apr 24 2024 Saturday...another low pressure system is forecast to move into the area from the southwest during the late afternoon and overnight hours. Easterly winds around 15 mph during the morning slowly back to the northeast around 20 mph late in the day, becoming northwesterly at 15 to 25 mph with higher gusts after midnight. Shower/thunderstorm chances increase through the day from west to east ahead of the approaching low with 40%-90% pops (east to west). Overnight, we'll have 50%-90% chances for showers/thunderstorms due to wraparound precipitation behind the low. With above normal precipitable water values, locations generally north of I-70 could see 24 hour rainfall amounts in the 0.50 to 1.75 inch range, highest in Yuma county. High temperatures are forecast to be in the lower 60s to middle 70s with low temperatures in the middle 30s to middle 40s. Sunday...as Saturdays storm lifts northeast and away from the area, we'll continue to be impacted by wraparound showers/thunderstorms during the day. Precipitation chances range from 20%-40% south of Interstate 70 to 50%-60% near the KS/NE border. Overnight, rainfall chances will have ended. High temperatures are forecast to be in the middle 50s to middle 60s with low temperatures in the middle 30s to around 40. Breezy/windy northwest winds are expected during the day with gusts up to 35, maybe 40 mph. Presently, there is a 20% chance for thunderstorms during the night across Norton/Graham counties. This seems tied to increasing moisture in the 850-500mb layer moving into those areas from the south and interacting with a strengthening low level jet. Monday...near zonal flow is forecast by the GFS/ECMWF/GEM/GEFS models. Presently, the forecast is dry. However, GFS/GEM 700-500mb relative humidity forecasts due show a disturbance moving across the area from very late in the afternoon through the evening hours, possibly supportive of some mention for showers/thunderstorms. Will have to watch how this develops over the coming days. High temperatures are forecast to bounce back up into the 70s with low temperatures in the 40s. Tuesday...broad upper level ridging is forecast to be over the area. 850mb temperatures from the GFS/ECMWF/GEM models continue to rise, supporting highs in the upper 70s to middle 80s, possibly even warmer if the GFS and ECMWF 850mb temperatures are realized under typical mixing. Low temperatures are forecast to be in the middle 40s to middle 50s. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 1059 PM MDT Tue Apr 23 2024 VFR conditions are expected over the KGLD and KMCK terminals through the 06Z TAF period. Light rain showers, possibly remaining as virga, will move east between the terminals this evening. Confidence is low that there will be any precipitation over the terminals, hence the lack of mention in the TAFs. Winds over KGLD will be increasing after sunrise Wednesday with southerly winds gusting up to 25-30 kts from 17Z to 00Z. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...Fire Weather Watch from Thursday afternoon through Thursday evening for KSZ013-027-028-041-042. CO...Fire Weather Watch from Thursday afternoon through Thursday evening for COZ253-254. NE...None. && $$ SHORT TERM...KAK LONG TERM...99 AVIATION...KMK